7

There were some detail changes due to adjustments in the storm track, which mostly affected central/northern PA, southern VA and the Delmarva Peninsula. Higher confidence in the higher snow totals brought some upscale changes to northern VA.

It’s still a low confidence forecast overall, with both upside and downside risks across most of the impacted region.

So here we are with another complicated setup and poor model agreement leading to a low confidence forecast. The good news is it looks like DC is finally going to get a decent storm! It only took until March…

Anyway, right now it looks like the biggest risks are along the coast and in PA and southern VA. I’ll save some of the more intricate details for the final forecast, but there is going to be some serious issues with the rain/snow line in the lower-total areas to the south, with precip. shield concerns across PA, NJ and southern NY.

There is also some upside risk west and a little north of DC, where strong banding will likely occur somewhere in there. The other big question is with the coastal low track and whether or not the more northerly GFS and bring higher snow totals to PA/NJ northward or if the more conservative Euro wins out in those areas. In that case, I decided to lean a bit more towards the Euro with the lower totals.

Some strong, gusty winds are possible east of the mountains north of the VA/NC border.

Just going to start off by saying that forecast confidence is lower than normal. Miller B type storm will form up late tomorrow into Friday and will initially cause mixing/temp issues across the more southern areas. As the coastal intensifies, banding on the back edge of the system could bring locally higher totals from central PA to NJ, NY and maybe even down into northeast MD and northern DE. There’s plenty of risk in either direction, especially across central PA into NJ and NYC/LI.

I didn’t try too hard to figure out contouring based on strict temperature and boundary layer issue areas since there is not enough certainty to really go into that much detail yet. That’s a job that is best saved for tomorrow’s update.

Made some changes to bring things a bit further east in general. I took out the 4-8 inch contour due to uncertainties in the forecast, but I do think there will be localized 4-8″ totals in eastern PA and western NJ. Confidence in the forecast is normal to slightly below normal.

Here we go with another early start to winter… but early start for who, exactly?

Well, the mountains already got a shock to the system last week as Sandy dumped as much as three feet or more of snow across West Virginia. This time around, it looks like the coastal areas will cash in more as those out west are left to deal with whatever remains of what they got last week. The latest model runs have (thankfully) converged on a somewhat reasonable solution for mid-week’s snow.

Despite the recent convergence, forecast confidence is still lower than normal as small shifts in the storm track could potentially lead to big shifts in the snow zone.

Quite a trying forecast, but overall it wasn’t a complete loss. Verified the mountain areas and highest totals fairly well, but the more heavily populated areas left much to be desired. Looking back, I could have been less generous with the 2-4 inch range in northern MD and southeastern PA, but other than that and bringing the 1 inch cut-off further north in MD I don’t see much that I could have done to change my overall thinking for this event.

The changeover from rain to snow was fairly messy east of the mountains, and most did not even transition to 100% snow. On top of that, the snowfall ended more abruptly and sooner than I had expected, which prevented the stronger cooling to make it to the surface in tandem with the back edge of the heavier precipitation. That slightly warmer boundary layer is what turned 1-4 inches into little to no accumulation.

Going to be a little generous and give myself a C- overall, though it wouldn’t take much convincing to push that to a D+ considering the bust in south-central/southeastern PA and MD and the western edge of the snowfall.

Had to make some big changes in the northern areas… the boundary layer temperatures did not cool off as much as I thought it would on the models in addition to a quicker end to the snowfall.

I think that a couple of areas will be able to top out just above 8 inches in the mountains, so I left a small area over some of the WV/MD pandhandles.

Snowfall totals should not get hurt too much after the transition to snow finally occurs as a small period of sleet during the transition could/should provide a decent base layer for the snow to accumulate on. Keep eyes and ears peeled for the possible thundersleet/thundersnow during the transition from rain, especially from the northern VA/DC region up through central PA.